A generic diagram of a slope in a jointed rock mass that is threatened by a planar block slide is shown, in the sketch. Although not shown, bench height is 55 ft (16.76 m).

Given that Mohr–Coulomb failure criteria apply, the clay-filled joints constitute 93%

of the potential shear failure surface, no tension cracks have yet appeared and:

1 slope height                          H =? ft (m);

2 failure surface angle             α = 32◦;

3 slope angle                           β = 49◦;

4 friction angle (rock)              φ_r = 38◦

5 cohesion (rock)                     c_r = 1000 psi (6.90MPa);

6 friction angle (joint)             φ_j = 27◦;

7 cohesion (joint)                    c_j = 10 psi (0.069MPa);

8 specific weight                     γ = 158pcf (25.0kN/m³);

9 tension crack depth              h_c = 0.0 ft (m);

10 water table depth               h_w = 0.0 ft (m);

11 seismic coefficient              a_o = 0.00;

12 surcharge                            s = 0.0 psf (kPa)

Find the maximum pit depth possible without drainage.

Transcribed Image Text:

WT he